Recently in one of our more productive company meetings the question was debated whether firearms could be fired in space. One bright participant in the conversation persisted that firearms could NOT be fired due to zero oxygen level. My suggestion to him was not to stand in the line of fire
while testing.
Wisdom on this subject would be appreciated.
Explosives contain their own oxydizing agent. Otherwise oxygen from air won’t be able to get to the reaction site fast enough.
I think the only possible problem you’ll face is the effect of vacuum on moving parts. Most lubricants evaporate in high vacuum, and if the moving parts are made of the same material, the contact point can cold-weld and seize up. I have no idea if that would be a problem with firearms though. Also, if you’re in free-fall or low gravity, the effect of recoil will be much greater.
That’s how I understand it.
The only “explosive” in ammo is in the primer which explodes (just a bit more than a cap gun) when the fireing pin or hammer strikes it. The primer lights the powder, which also contains oxygen, and the expanding gas from the burning powder pushes the bullet through the barrel.
According to the Grease Man, guns in space are necessary! - When have ya ever watched a movie about space and did NOT see gunplay? 
Steve
Cartridges should function as normal in space. Smokeless powders are based upon nitrated cellulose, which contains its own oxygen in the nitrate groups.
There are a few other considerations which may cause current guns to malfuntion in space:
As scr4 said, there may be problems with oil vapourising in the zero pressure removing all the lubrication.
“Cold welding” or “vacuum welding” might occur, where moving metal parts fuse together. In theory, the normal healthy layer of oxide and crud found on metals is scraped off by the metals sliding past each other, but can’t reform due to the super-clean space vacuum, allowing the metals to bond.
From what I’ve read, vacuum welding was a cause of concern in satellite design and other space missions, but hasn’t been confirmed by observation.
Recoil is going to make you move, and if you’re in orbit the bullets are going to be whizzing around at undiminished speed for a long time. Rifling is going to gradually impart rotational momentum to you, so a long burst on a machine gun may leave you in a spin.
If you’re carrying a gun from a pressurised to an unpressurised situation, say through an airlock, the trapped air in the cartridges may force the bullets out. Similarly, if you go from the vacuum of space into a pressurised situation, the vacuum in the surviving cartridges may cause the bullets to be forced further in or even collapse the cartridge (probably unlikely - I think cartridges are strong enough to take it.)
None of these are insurmountable problems. A gun could be designed for space use with minimal lubrication requirements, ceramic components, teflon or graphite lube. Solid grain propellant blocks with no air space in the cartridges would prevent pressure changes being a problem. Self-destroying bullets, e.g. a slow-burning fuel-oxidant pellet with only gaseous products (say, 20 seconds to burn completely) will prevent you from accidentally taking out a satellite on the other side of the planet. We already have muzzle brakes to take off some of the recoil. We could probably dispense with rifling in space since there are no aerodynamic forces to make bullets tumble. (This would mean that a “space gun” is going to be less accurate and effective fired in an atmosphere.) Alternatively, have two barrels rifled in opposite directions!
i wunna stand in the way - the atmosphere there is less friction and the bullet has more kinetic energy and is more
or less like those HV bullets than can go right through human bodies without significant stopping power (HVs are modified to tumble when they hit meat or what not to cause
more stopping power such as hollow pointing them)
Welcolm, juscuz. Your “company” doesn’t happen to be the Joint Chiefs of Staff, does it? What with the new boss there and all . . .
No “West Wing” antics here!
It’s no secret, I am not a rocket scientist I just don’t think that ammunition discharge is dependant on oxygen. Gases created and expanded during explosion creates the force as a propellant for the bullet.
How do rocket boosters and propellants work in zero oxygen environments?
Nothing magic about oxygen. You just need a chemical reaction which produces energy and gaseous products. Having said that, fuel-oxygen reactions are commonly used, largely because the reaction products are less nasty than some of the alternatives.
Propellants can be mixtures, e.g. gunpowder is a mixture of charcoal and sulphur fuels and potassium nitrate oxidiser. The potassium nitrate decomposes with heat to release oxygen gas, which then reacts with the charcoal and sulphur. The reaction products are complicated but include a good quantity of carbon dioxide gas, which provides the propulsion.
A non-oxygen propellant mixture is zinc powder and sulphur, which react together when ignited to produce zinc sulphide vapour. It’s popular with rocket hobbyists, but not so great for practical, useful rockets.
Propellants can also be molecules which contain a fuel and an oxidiser component. Cellulose is a natural polymer, the major constituent of wood, cotton and paper, and obviously can be burned. It acts as the fuel. Nitrating it adds oxygen in the form of attached nitrate groups, so it can now be burned without an external source of oxygen. Nitrocellose is the basis of many if not all smokeless powders for firearms, and it’ll burn in a vacuum.
The question of firing guns in space is not academic. Yes, it’s true: They’ve got irons up there.
The survival kit contains signal flares, too. Oh what fun they could have in that tin can of an ISS!
This is easy enough to demonstrate without getting orbital. Firearms fire just fine under water, which is equivalent to space in terms of providing oxygen to the reactants. It’s not good for the weapon, but it’s even worse for the low-tech who wants to stand in front of the barrel to prove a point.
Here is a thread Shotguns in Space that is about this subject.
I thought that “Cold welding” was only possible if the two surfaces were perfectly smooth. i.e. almost frictionless. Am I thinking of something else.
I think “clean” is more important than “smooth”. Clean in the sense that the surfaces must consist of exposed metal atoms only, without even an adsorbed layer of gas molecules. Getting a good enough vacuum to achieve this on Earth is expensive.
It’s frustratingly difficult to find good articles on the subject on the internet. Here’s one by Japanese authors proposing an experiment to confirm the existence of cold welding in space:
http://york-me.eng.hokudai.ac.jp/spacesystem/satellite/mission.htm
I find it interesting that the experiment proposes erecting an inflatible disc in orbit to create an even higher vacuum in its wake than is already present. Just how good a vacuum do these guys want?
I think it’s both. If it isn’t smooth, the contact area is small and only small spots of weld are formed which can be easily broken. The biggest danger is where two flat surfaces slide or rub against each other - the rubbing cleans and smoothes the contact surface.
Hmm, I thought “cold weld” happens in everyday situations too. If you use a clean stainless steel bolt on a stainless steel part and forget to lubricate the thread, it will bind and become impossible to remove - isn’t that basically the same phenomenon?
As for using a shield to create high vacuum, it’s already been done on the shuttle. The Wake Shield Facility flew on the Space Shuttle in 1994. It was designed to achieve a pressure of 10^-13 torr. Without the shield, the pressure at Shuttle altitude is about 10^-7 torr, so the shield provides a vacuum a million times better.
Don’t know. I wasn’t able to find a clear definition of “cold welding” with a Google search, and how it is distinguished from friction welding. I think the point is that it is much easier to achieve clean surfaces in a high vacuum, especially since a freshly created metal surface can’t oxidise, so the risk of welding occuring accidentally with smaller contact forces is presumably greater.
I haven’t experienced the problem with stainless steel bolts myself, but maybe I’ve never used a really clean one or tightened it up enough. I’m quite surprised since stainless steels have a permanent chromium oxide layer on their surface. Maybe the binding is due to a different mechanism?
Thanks for the wake shield link!
I think one gets into trouble when st. steel hardware is used with aluminum or mild steel stuff.
from http://www.boltscience.com/pages/faq.htm
Q. What is meant by the term ‘galling’?
A. Galling is a severe form of adhesive wear which occurs during sliding
contact of one surface relative to another. Clumps of one part stick to the
mating part and break away from the surface. (Galling can frequently occur
when both the nut and bolt are zinc coated.)
As far as welding in firearms, the lead is soft enough to provide lubrication, it’s used in bearing materials for it’s lubricating properties.
This thread reminds me of what may be an engineering UL of sorts, which is that jewelers and producers of gold bars quite frequently see cold welding as the clean, non-corroded flat pure gold surfaces come into contact with each other. Has anyone heard of this being a problem with gold?